Telephone system



Patented June 1, 1926."

QHARLESQ'L. eoonnumror NEW Yong, Y.',., essienon o .wnsmnnn ELnc'rnIe COM- P N!INOORPQnATEnJENEW Yonx, A con-ronnrron' oennw Yonx; c

Applicationnled July-21, 1921. Serial no; 4863441. 7

for paging dictation purposes, or the like,

may beautoma-tically connected to a system; designed for use with ordinary subscribers substations;

- A further, objeetof the invention'is to prevent the ringingcurrent ordinarily-supplied to the substation circuits ofen autoinn-tic system from actuating a. loud speaker substation. e

A furtherobj'ect of the invention-1s to provide a telephone substation haying a loud speaking receiver and a sensitive transmitter,

which-will be freeffrom singing or howling due tothe interaction of the instruments The above and other objects of tlie inven tion illhe more fully understood from the following detailed description and cla ms taken in connection with the accoinpany1n'g drawing inwhich'the figure illustrates die grammaticetlly system employing-the nvention; Referring tothe drew'ing" by reference,

numerals, e subscrihers subst'e'tion'set 10 of a well-known form haying ai ditliii switch 12 is adaptedtobe connectedth roug a loopcircuitij 14;" a trunk finder switch 16, and a connector switclrfilS, comprisinga; side switch '20 and brushes 22*; to the loud speak ing substation circuit' 24. The" above switches are a part are well -known formiof automatic system clifi'ering. I only in' minor detuils'frointhe system shown in my Patent scribers stations similar 'tothe statiOnlfO No. -1-,231,-01e,-unevenness; 191-7; for "my; toinatic telephone exchange; system. c Th s systenrmay be a localtelephione'system such as one installed in a hotel,business house, or the; like, and comprises a numbe of; sub-4 wh-ich have bells or siinilar'cal-ling devices- Whichf are automatically" 'energizedi when tn substation has-beenselected'lj I i accordance with this invention one or more substettions similar to the one sho wn'et 2.4 ere adapted to p be connected to J by; the

but may be --'used in e city exchange or elsewhere if desired.

Subst'etion'2l comprises a loud speaking receiver'26, a sensitive transmitter 28; which ni s y, forexa1'11ple,'be of the type used in d10- tegraph Work, 'and the substation circuit is an adaptation ofthe circuit; shown in Fig. 5 c v 'ofCsnipbell.Paten't No: 1,254,472, dated in an artificial "line circuit comprising the ertificiatll1ne--3i'. The transnntteninstead ofbeing connected directly in the conductor joining the common term-inals of windings @O'end 31, as in the above Campbell patent, is-inductively connected theretoiby a trans- ,former 362 For the purpose of direct current supply, the transmitter is also directly ducts-nee 40 and-1a shunt condenser 38, which providesa pet-h for. the alternating coinponent of the transmitted currents; 2 The inductance 40" may be of high linpedunce to oice currents butshould be ofjlow iinpedconnected to the line through a double in anceto ringingcurrents, esiwill be appar ent from the description of operation below;

By this arrangement, the transmitter is in, a,

local circuitwith respect to" talking currents,

but ztd'ap'ted' to be connectedto' the line for the purpose of common batterysupply. As explained in theab'oye Campbell patent, curren-tsfgenerated; in the transmitter divide hetween' the lineand theartificial line M ini such a- Way thetno'response is: produced: in

the IieceiVerQG. This is Very important, for the reason that ifside tonje were presenh the transmitter 28' would pick, up room noises; tone would be produced in the loud speaker end'singing wouldresult w r p I The arren'genient of the relsysjof the con nector switch 18 will be bestj understood. in

which would again react; onthe transmitter,

connection with; their operatioln; which is: as follo'WsrVVhen the receiver at substation? 10' isirenioved frojmthe hook, the trunk find erjsivitch indicated et 16 is set in operation In a; manner Welliunderstood 1n. the art and makes connection to en idle connector switch;

18, such as" the emer es-in thegdrawingi 11 pure-tn usedttojctll ztn As soones" connection is made, cu rent s r v my. st e i e em d iitei e; m eneiiinesuesse in alers'lese lmn s; eat? is to te transmitter is ill;

substation 10. Armature 45 is drawn up energizing slow-acting relay 47, the armatures 48 and of which are then drawn up. In the circuit shown, it is assumed that no substation to be called will have a number having more than two digits. The subscriber now dials the first digit of the number to be called. Armature 415 of relay 4A is released as many times as there are units in this digit. Armature l9 of slow-acting relay 47, however, does not release, and it may be stated here that this contact as well as contact i8 remains up until the party at substation 10 hangs up his receiver. The vibrations of armature 45 intermittently close a circuit from ground through armature 49, brush 20 primary magnet 51 and battery thus actuating the primary magnet 51 and stepping up the brushes 22 the desired number of steps. The movements of armature 45 also supply an intermittent ground to the slow-acting relay 58, causing its armatures 55 and 57 to be drawn up. Armature 57 closes a circuit through the escape magnet 59, closing the contact 61 in the circuit of the source of ringing current This circuit, however, is open at the brush 20 and there is no flow of ringing current. As soon as the subscriber has ceased dialing, ground is disconnected from relay 53, thus deenergizing this relay and escape magnet 59, which in deenergizing steps the side switch 20 to its second position. It will be noted that the side switch 20 comprises four brushes 20 20 20 and 20. The subscriber now dials the second digit, and each time the armature a5 makes contact with its back contact an impulse is sent to the secondary magnet 65, which is now connected to the brush. 20. This steps the brushes 22 around to the terminals of the substation desired to be called. If the substation is busy, there will be ground present on contact 67 due to a connection from brush 20 to ground 68 of some other connector switch. A circuit will thus be connected from ground to contact 67, brush 20 armature 55, OH normal switch 70, which was closed at the first movement of brushes 22, through the release magnet 72, closing armatures 73 and 74 of the latter. Closing the armature 73 causes busy tone from the source 75 to be sent out on the line, indicating to the calling party that the called substation is busy. Meanwhile the release magnet 72 restores switch 18 and its associated side switch 20 to normal position and contact 7% keeps closed a locking circuit extending through armature 48, battery 77 to ground, so that the busy tone is continuously applied until the subscriber releases armature 48 by hanging up his receiver.

If the substation 24 is not busy, as soon as the subscriber ceases dialing, relays 53 and 59. which have been energized as in the first dialing step, are again deenerg'zed and the side switch 20 is moved to its third po sition. Ground is thus immediately again connected to relay 53 through armature 45 and brush 20 and again causes armature (S1 of escape magnet 59 to be drawn up. The circuit for ringing current is now completed through armature 61, relay 79, brush 20 transmitter 28, brush 20 and armature 425. In the case of an ordinary substation circuit, the impedance of the circuit when tic receiver is on the hook is large, and the ringing current supplied is of such a small value that relay 79 is not actuated until the subscriber takes down his receiver closing a low impedance path to the transmitter, atter which relay 79 draws up its armature 80, breaking the circuit through the escape magnet 59. The substation 2% is, however, de-

signed so that a low impedance path to 'ringing current always exists through the transmitter 28, and at this stage in the operation oi the circuit, relay 79 is actuated as soon as ringing current begins to how, and as soon as armature 80 is drawn up, and 61 released, the ringing current is tripped. The deenergization of escape magnet 59 also moves side switch 20 to its fourth position. Brushes 20 and 20,, then connect the substation 24: to the line and to a source of talking H current 82, which supplies current through a retard coil 83.

The substation 2 1 may be located in a room containing a number of persons, for example, a room in which a large clerical force is seated, or in a hotel rest room, or the like. The calling party simply calls the person with whom he wishes to speak by name, the loud speaking receiver 26 giving suiiicient volume of sound to be heard in any part of the room, and the called person may reply from his position by reason of the fact that transmitter 28 is extremely sensitive, or it he desires, he may approach the substation and reply directly into the transmitter 28. As soon as the conversation is completed, the party at substation 10 hands up his receiver, breaking the circuit through relay 4E4, releasing armature 45 which in turn breaks the circuit through relay 47, releasing armatures 48 and 49 and connecting ground through armatures 45, 41-9, 48, oii' normal switch 70 to release magnet 72. Re lease magnet 72 in a manner well understood in the art restores the switch 18 to normal position and as soon as the switch has reached normal position, oft normal switch 70 is opened, thus breaking the circuit for release magnet 72 and the connector switch 18 and associated switches are in condition to be selected for another call.

While the invention has been illustrated in connection with a certain type of automatic system, it is obvious that it may be preventing sidetone in said receiver, andmeans operable from a distant point on said line for connecting said substation tosaid line. b I I a 2. -A telephone system comprising a plurality of substations, automatic means controllable by a calling party for interconnect' ing twoof said substations, at least one of said substations comprising a loud speaking receiverand a sensitive transmitter, said transmitter being permanently connected in bridge across the substation line conductors.

3. A telephone system comprising a line, a second line, means for interconnecting said lines, a source of current in said first line,

aloud speaking receiver and a sensitive transmitter, said transmitter being permanently connected in circuit with said second line with respect to direct current -from sald source but ininductive relation there with with respectto voice currents, and

means toprevent impulses produced by said.

. transmitter from energizing said receiveix.

4. A telephone system comprising aline, a second line, means for interconnecting said lines, a source of current in said first line, a loud speaking receiver and a transmitter,

said transmitter being permanently connected to said second line with respect to voice currents anddirectly connected to said line with respect to direct current from said source, and meansincluding a balancing network to prevent impulses produced by said transmitter from energizing said re-,

ceiver.

5. A telephone system comprising a line, a second line, means for interconnecting said lines, a source of current in said first line,

a loud speaking receiver and a sensitive transmitter, said instruments being permanently connected to said second line to receive and transmit telephone currents substantially solely by induction, and means for to said transmitter. i I p *6. A telephone system comprising an automatic switch, a source of current'i'n said switch, a loud speaking receiver and a sensi tive' transmitter accessible to saidswit-ch via.

a set of terminals, said transmitter which is permanently connected to saidterminals be- .ing,'wlieii a connection is established, in-

ductively connected in circuit ,with said switch with respect to voice currents" and di- 'rectly connected 11'1 clrcuit with said-switch with respect to direct current from said source, and means including abalancing network to prevent impulses produced by said transmitter from energizing said receiver. In witnesswhereof, I hereunto subscribe my name this 20th day of July A. 1)., 1921.

CHARLES L. GOODRUM.

supplying current from said source directly 

